JPH06268299A - Pumping light source for laser - Google Patents

Abstract

PURPOSE:To reduce the labor hour for assembly and adjustment by a method in which pumping means independently condense the pumping light received from a corresponding light emitting means, and grating couplers independently emit the pumping light condensed by the corresponding pumping means to a certain point in the space. CONSTITUTION:In the light source for laser pumping, a plane light waveguide path 32 is formed on a substrate 31. The plane light waveguide path 32 is formed on one surface of the substrate 31, and a plurality of pumping LDs 33 outputs laser light into the plane light waveguide path 32 and to a central point 32b in the plane light waveguide path 32. Then, pumping lenses 34 independently condense the laser light received from the corresponding pumping LD 33, and grating couplers 35 independently emit the laser light condensed by the pumping lens 34 to a focal point 37 in the space. Miniaturization is achieved by providing a plurality of optical systems on one substrate 31, and the emitted light obtained from each optical system is focussed to the focal point 27 to provide a large output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pumping light source for a laser used for pumping a solid-state laser.

[0002]

2. Description of the Related Art In recent years, in a solid-state laser used for laser processing or laser distance measurement, when exciting the laser medium,
Excitation light sources that perform optical excitation are widely used. Figure 5
It is a figure which shows the structure of this kind of solid-state laser.

This solid-state laser is a semiconductor laser (LD).
The laser light emitted from the laser beam passes through the collimating lens 2 and the anamorphic prism 3 and is condensed by the condensing lens 4. The laser rod 5 is made of Nd: YAG, for example.
Incident on. The laser rod 5 is optically excited by the laser light incident from the condenser lens 4 to generate a laser light, and the laser light is output through the output mirror 6. In addition,
The oscillation output of this type of solid-state laser is continuous wave (CW).
Although several watts are commercially available, there is a demand for higher output and smaller size. Here, when the solid-state lasers have the same configuration, it is necessary to increase the output of the pumping light source in order to increase the output.

However, in order to increase the output of a semiconductor laser as a pumping light source, there is a limit with a single active layer. For this reason, a phase-locked type in which the active layers are arranged in an array is used. However, when the number of active layers forming the array increases, the laser beam shape at the end face of the semiconductor laser becomes an ellipse and the beam has a large aberration. Therefore, there is a problem in that it is difficult to efficiently oscillate the solid-state laser by condensing the light into an appropriate shape.

On the other hand, in order to solve the above-mentioned problem, FIG.
A solid-state laser having the configuration shown in FIG. In this solid-state laser, a plurality of LD modules 11 with MM fibers (multimode fibers) are bundled into an optically coupled fiber bundle 12, and the output from the bundle end 12 a is passed through a condenser lens 13 and a mirror 14 to form a laser rod. It is incident on 15. The laser rod 15 is optically excited by the laser light incident from the condenser lens 13 to generate a laser light, and the laser light is output through the opening 16 and the output mirror 17. The output from the bundle end 12a is the excitation light of the solid-state laser.

Here, the LD module 1 with MM fiber
As shown in FIG. 7, one of the laser lights output from the two semiconductor lasers 21 is a collimator lens 2
2, prism circulator 23 and half-wave plate 2
And enters the polarization beam splitter 25 through the other side, and the other side into the collimating lens 22 and the prism circulator 2.
It is incident on the polarization beam splitter 25 only via the beam splitter 3.
The polarization beam splitter 25 combines and emits the laser beams incident from the half-wave plate 24 and the prism circulator 23. The laser light combined by the polarization beam splitter 25 is collected by the condenser lens 26 and the FC connector 2.
It is incident on the multimode optical fiber (MM fiber) via 7. In the solid-state laser having such a configuration, it is possible to increase the output of the pumping light source by increasing the number of LD modules 11 with MM fiber.

[0007] For example, at Sony Corporation, the output is ~ 9 W, the diameter ~ 4 by using seven LD modules 11 with MM fiber.
It has been reported that a circular spot with an output of 24 W and a diameter of 700 μm was obtained as excitation light by the LD module 11 with 00 μm or 19 MM fibers.

[0008]

However, in the above-mentioned pumping light source, the L with MM fiber having a large number of parts is used.
Since a large number of D modules 11 are required, there is a problem that the pump light source becomes large in size and expensive.

In addition, it takes a lot of time and effort to assemble and adjust each module and the whole pumping light source, and when the cost is included, the cost of the entire apparatus becomes too high.

The present invention has been made in consideration of the above-mentioned circumstances, and reduces the trouble of assembling and adjusting, and is small and has a large output.
It is also an object of the present invention to provide an excitation light source for a laser that can be manufactured at low cost.

[0011]

In order to achieve the above object, a pumping light source for laser of the present invention collects pumping light and outputs output light at a predetermined level or more, and a substrate,
An optical waveguide formed on at least one surface of the substrate, and an end face portion provided on the outer peripheral side of the substrate so as to be coupled to the optical waveguide, and the excitation from the end face portion toward a predetermined position in the optical waveguide. A plurality of light emitting units that output light, a light collecting unit that is provided in the optical waveguide, and that individually collects excitation light output from the light emitting units toward the predetermined position, and a light collecting unit that is provided in the optical waveguide. And a grating coupler that individually emits the excitation light condensed by the condensing unit toward a certain point in space.

[0012]

Therefore, in the excitation light source for laser of the present invention, the optical waveguide is formed on one surface of the substrate, and the plurality of light emitting portions direct the excitation light into the optical waveguide toward predetermined positions in the optical waveguide. Then, the light collecting section individually collects the excitation light received from the corresponding light emitting section, and the grating coupler individually emits the excitation light collected by the corresponding light collecting section toward a certain point in space. Therefore, it is possible to reduce the trouble of assembly and adjustment, and to achieve a small size and a large output.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 3 are a perspective view, a sectional view taken along the line AA of the drawing, and a plan view showing the structure of a laser pumping light source according to a first embodiment of the present invention.

In this laser excitation light source, a planar optical waveguide 32 is formed on a substrate 31. The planar optical waveguide 32 is
Of a plurality of directions (hereinafter referred to as plane convergence directions) from the outer peripheral portion 32a toward the center point 32b, the center points 3 are
A pump LD 33 as a light emitting portion, a condenser lens 34 as a condensing portion, and a grating coupler 35 are provided along four plane converging directions having an angle (hereinafter, referred to as a central angle θ) sandwiching 2b as 90 degrees. Four optical systems are arranged.

Here, the pumping LD 33 has an output end of laser light (excitation light) attached to the LD mount 36 on the outer peripheral side of the planar optical waveguide by an end face direct coupling method, and has a center in the corresponding plane converging direction. It has a function of outputting laser light as an optical axis to the condenser lens 34 through the planar optical waveguide 32. The pumping LD 33 has an adjustable output, and its output is adjusted in advance so that the intensities of light emitted from the respective optical systems are equal.

When the condenser lens 34 receives the laser light output from the exciting LD 33 and diverged by the plane optical waveguide 32, the condenser lens 34 condenses the received laser beam through the plane optical waveguide 32 to the grating coupler 35. For example, various lenses such as Fresnel type, diffractive type and mode index type lenses can be used. The Fresnel type is suitable for downsizing of the system because it occupies a small area.

In the grating coupler 35, a linear grating is formed so that the grating period is continuously shortened by an appropriate amount of change in the beam propagation direction, and the opening is circular. That is, when the laser light condensed by the condenser lens 34 is received, the emitted light is emitted to the space on the planar optical waveguide at different emission angles corresponding to the respective grating periods, and the predetermined condensing point in the space is obtained. It has the function of focusing light on 37. The emitted light at the condensing point 37 has a spot shape of a circle corresponding to the shape of the opening, and is guided to the solid-state laser resonator 38 to excite the laser medium in the resonator.

The condenser lens 34 and the grating coupler 35 are formed integrally with the plane optical waveguide 32. Further, the creation parameters of the condenser lens 34 and the grating coupler 35 are set so that a plurality of emitted lights have a sufficient working length and light intensity in a solid-state laser resonator (not shown) to maximize the excitation efficiency of the solid-state laser. Is designed. The manufacturing parameters are, for example, the condensing lens 3
In 4, the focal length and the aperture length are used, and in the grating coupler 35, the grating shape, the grating period, and the curvature are used. Next, the operation of the laser excitation light source configured as described above will be described.

The pumping LD 33 outputs laser light to the plane waveguide 32 from the outer peripheral portion 32a of the plane optical waveguide 32 toward the center point 32b. This laser light becomes a divergent wave while being confined in the thickness direction of the planar optical waveguide 32, propagates in the planar optical waveguide 32, and enters the corresponding condenser lens 34. Each condenser lens 34 condenses the laser light, which is incident as a divergent wave from the excitation LD 33, on the grating coupler 35. Each grating coupler 35 emits the laser light condensed by the condenser lens 34 to the space on the optical waveguide 32 and individually condenses it at the condensing point 37 in the space.

Therefore, at the condensing point 37, the emitted lights respectively emitted from the four grating couplers 35 provided in the plane optical waveguide 32 are condensed and overlapped, and a high output minute circular spot is formed. To be done.

At this time, since the four optical systems are arranged along the plane converging direction so that the central angles θ are equal to each other, the light intensity of the circular converging spot at the converging point 37 is spatially uniform. , And is symmetric. Further, this circular focused spot is guided into the solid-state laser resonator 38 to optically excite the solid-state laser.

As described above, according to the first embodiment,
The planar optical waveguide 32 is formed on one surface of the substrate 31, and a plurality of pumping LDs 33 are provided at the center point 32b in the planar optical waveguide 32.
Laser light is output into the planar optical waveguide 32 toward
The condenser lens 34 individually condenses the laser light received from the corresponding LD for excitation 33, and the grating coupler 35 directs the laser light condensed by the corresponding condenser lens 34 to the condensing point 37 in the space. It is emitted individually.

Therefore, since a plurality of optical systems are provided on one substrate 31, the size can be reduced and the emitted light obtained from each optical system can be condensed at the condensing point 37 in the space. Therefore, the output can be increased.

Since the condenser lens 34 and the grating coupler 35, which are optical components other than the exciting LD 33, are integrally provided in the planar optical waveguide 32, only the exciting LD 33 needs to be assembled and adjusted. As a result, it is possible to reduce the labor for assembling and adjusting and reduce the assembling and adjusting cost.

Further, according to the first embodiment, the light output can be efficiently guided into the solid-state laser resonator 38 as a spatially symmetrical focused spot with a simpler structure than the conventional one. Therefore, the LD-pumped solid-state laser can be downsized and the output can be increased.

Next, a laser pumping light source according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a cross-sectional view showing the structure of this laser excitation light source. The same parts as those in FIG. 1 are designated by the same reference numerals and their detailed description is omitted.
Here, only different parts will be described.

That is, in this embodiment, the substrate 31 is made of a material that allows the laser light of the pumping LD 33 to pass therethrough, and the flat optical waveguides 32, 32 are formed on both surfaces of the substrate 31 as in the first embodiment. 32 'and pumping LD 33, 3
3 ', condenser lenses 34, 34', and grating couplers 35, 35 '.

Of the grating couplers 35, 35 'provided on both sides of the substrate 31, the grating coupler 35' on the surface not facing the converging point 37 is the LD for excitation.
The laser light received from 33 'through the condenser lens 34' is emitted from the plane optical waveguide 32 'to the substrate 31, and the emitted light is passed through the substrate 31 and another plane optical waveguide 32 to a predetermined condensing point in the space. It has the function of focusing light on 37.

Further, in order to collect all the emitted light emitted from each optical system on both surfaces of the substrate 31 at the condensing point 37, the optical waveguides 32 and 32 ', the condensing lenses 34 and 34' and the grating coupler. The production parameters of 35 and 35 'are adjusted.

Here, on both surfaces of the substrate 31, the emitted light is emitted from each of the plurality of optical systems, and the emitted light is condensed at the condensing point 37 in the space and overlaps with each other.
One circular focused spot is formed. Thereafter, similarly to the first embodiment, the solid laser is optically excited by this circular focused spot.

As described above, according to the second embodiment,
As in the first embodiment, the planar optical waveguide 3 is formed on both surfaces of the substrate 31.
By providing 2, 32 'and a plurality of optical systems,
Since the effect of the embodiment can be obtained, and the number of the excitation LDs can be arranged as compared with the first embodiment, the size of the excitation LD is about the same as that of the first embodiment. A light output can be obtained.

In the first embodiment described above, the case where the plurality of directions from the outer peripheral portion 32a of the planar optical waveguide 32 toward the central point 32b are the plane converging directions has been described. Even if it changes to arbitrary points, the present invention can be similarly implemented and the same effect can be obtained.

In the first embodiment, the case where four optical systems are arranged on one surface of the substrate 31 so that the central angle is 90 degrees has been described. However, the number of optical systems is not limited to this. Alternatively, even if the optical system is arranged such that the value obtained by dividing 360 degrees by the number becomes the central angle, the present invention can be similarly implemented and the same effect can be obtained.

Further, in the first embodiment, the central angle θ
However, not limited to this, even when the central angle θ is different, by appropriately designing and arranging the pumping LD, the planar optical waveguide, the condenser lens and the grating coupler, The present invention can be implemented in the same manner to obtain the same effect.

In the first embodiment, the LD for excitation is used.
Although the case where the end face of the optical fiber is directly coupled to the planar optical waveguide has been described, the present invention is not limited to this, and the end face of the pumping LD is coupled to the end face having the optical fiber, and the other end of the optical fiber is planar Even if the excitation light from the LD for excitation is coupled to the optical waveguide to enter the planar optical waveguide, the same effects can be obtained by carrying out the present invention in the same manner.

In the first and second embodiments described above, 1
The case where one condensing lens 34 is used for one optical system has been described, but the present invention is not limited to this, and the present invention is similarly embodied even if a plurality of condensing lenses are used for one optical system due to design requirements. Then, the same effect can be obtained.

Further, in the first and second embodiments,
The case where the shape of the opening of the grating coupler 35 is circular has been described, but the present invention is not limited to this, and the same effects can be obtained by implementing the present invention in the same manner even if the shape of the opening is square or another shape. You can

In the first and second embodiments, the case where the linear coupler is used as the grating coupler 35 has been described. However, the present invention is not limited to this, and a curved grating is used to make the convergence state in the optical waveguide plane. Even if the configuration is changed and the configuration is combined with a condenser lens, the present invention can be similarly implemented and the same effect can be obtained. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0039]

As described above, according to the present invention, an optical waveguide is formed on one side of a substrate, and a plurality of light emitting portions direct excitation light into the optical waveguide toward predetermined positions in the optical waveguide. The pumping light that is output and received by the light-collecting unit from the corresponding light-emitting unit is individually collected, and the excitation light that is collected by the corresponding light-collecting unit by the grating coupler is individually emitted to a certain point in space. Therefore, it is possible to reduce the labor for assembling and adjusting, and to achieve a small size, a large output, and a low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing the configuration of a laser excitation light source according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA showing the configuration of the laser excitation light source according to the embodiment.

FIG. 3 is a plan view showing a configuration of a laser excitation light source according to the same embodiment.

FIG. 4 is a sectional view showing the structure of a laser excitation light source according to a second embodiment of the present invention.

FIG. 5 is a diagram showing a configuration of a conventional solid-state laser.

FIG. 6 is a diagram showing a configuration of a conventional solid-state laser.

FIG. 7 is a diagram showing a configuration of an LD module with an MM fiber applied to a conventional solid-state laser.

[Explanation of symbols]

31 ... Substrate, 32 ... Planar optical waveguide, 32b ... Center point, 3
3 ... Excitation LD, 34 ... Focusing lens, 35 ... Grating coupler, 37 ... Focusing point, 38 ... Solid-state laser resonator.

Claims (1)

[Claims] 1. A pumping light source for a laser that collects pumping light and outputs output light at a predetermined level or higher, a substrate, an optical waveguide formed on at least one surface of the substrate, and an end face portion on the outer peripheral side of the substrate. Is provided so as to be coupled to the optical waveguide, and a plurality of light emitting portions that output the excitation light from the end face portion toward a predetermined position in the optical waveguide; A condensing unit that individually condenses the output excitation light toward the predetermined position, and the excitation light that is provided in the optical waveguide and that is condensed by the condensing unit is directed toward a certain point in space. An excitation light source for a laser, which is provided with a grating coupler that emits individually.